Please review: dtrace usdt

[Mark Johnston]

On Sun, Dec 15, 2013 at 07:30:19PM +0800, Prashanth Kumar wrote:
> 
> Dtrace doesn't properly process object file of relocation type SHT_REL, which is type
> in FreeBSD i386. The following patch checks for both relocation types SHT_REL and SHT_RELA, and
> calls matching update function.Tested usdt example program from (https://wiki.freebsd.org/DTrace/userland)
> in FreeBSD -10BETA1 - i386 and it works.

Hi Prashanth,

Thanks for the patch. I've committed a modified version of it as
r260051: http://svnweb.freebsd.org/base?view=revision&revision=260051

-Mark

> --------------------------------------------------
> --- dt_link.c	2013-12-15 14:24:37.000000000 +0400
> +++ /usr/src/cddl/contrib/opensolaris/lib/libdtrace/common/dt_link.c	2013-12-15 14:22:21.000000000 +0400
> @@ -1542,7 +1542,10 @@
>  			rela.r_offset = 0;
>  			rela.r_info  = 0;
>  			rela.r_addend = 0;
> -			(void) gelf_update_rela(data_rel, i, &rela);
> +			if (shdr_rel.sh_type == SHT_RELA)
> +				(void) gelf_update_rela(data_rel, i, &rela);
> +			else 
> +				(void) gelf_update_rel(data_rel, i, (GElf_Rel *)&rela);
>  #endif
>  
>  			mod = 1;
> -----------------------------------------------------------
> 
> prashanth
> --------------------------------------------
> On Wed, 4/12/13, Michael Harsch <michaelharsch at hotmail.com> wrote:
> 
>  Subject: Re: dtrace usdt
>  To: "Prashanth Kumar" <pra_udupi at yahoo.co.in>
>  Cc: freebsd-dtrace at freebsd.org
>  Date: Wednesday, 4 December, 2013, 11:13 PM
>  
>  Hi Prashanth,
>  
>  I've reproduced this on 10.0BETA4.  It appears to be
>  specific to i386;
>  the same test works fine on amd64.
>  
>  On Wed, Dec 4, 2013 at 3:29 AM, Prashanth Kumar <pra_udupi at yahoo.co.in>
>  wrote:
>  > Hi
>  > Tried running the dtrace usdt example code from freebsd
>  dtrace userland wiki page.
>  > (https://wiki.freebsd.org/DTrace/userland).
>  >
>  > If run standalone the program segfaults.
>  >  # ./db
>  > Bus error (core dumped)
>  >
>  > If run with dtrace
>  >
>  >   # dtrace -s db.d -c ./db
>  > dtrace: script 'db.d' matched 2 probes
>  > CPU     ID     
>               
>  FUNCTION:NAME
>  >   0  43245     
>         
>     main:query-start Query: SELECT * FROM
>  apples
>  >
>  > the program hungs after printing the first probe.
>  >
>  > Had to use the following command
>  >   # env WITH_DTRACE=1 make
>  >
>  > to build the program. Is there any other steps that i
>  have missed to make the program work?.
>  > This was tested on FreeBSD 10BETA1 - i386.
>  >
>  > regards
>  > Prashanth
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